Could tshark capture the de-encrypted packet when receiving ESP?

tshark
ESP

asked 2024-04-09 00:23:53 +0000

mzhan017
3 ●2 ●3

We encounter one problem: When using tshark to capture the packets on one interface(virtio_net). The tshark could capture one ESP packet, and also one packet without ESP header, that has been de-encrypted by kernel to plain packet.

How the tshark captured the second de-encrypted packet?

Thanks, Mark

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answered 2024-04-09 01:22:46 +0000

mzhan017
3 ●2 ●3

updated 2024-04-09 07:23:12 +0000

grahamb

flag of United Kingdom of Great Britain and Northern Ireland

23835 ●4 ●976 ●227 https://www.wireshark.org

Seems expected for tunnel mode, from code of kernel. xfrm_input

....
    if (x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL) {
        decaps = 1;
        break;
    }
....
    if (decaps) {
        if (skb->sp)
            skb->sp->olen = 0;
        skb_dst_drop(skb);
        gro_cells_receive(&gro_cells, skb);
        return 0;

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Asked: 2024-04-09 00:23:53 +0000

Seen: 119 times

Last updated: Apr 09

Could tshark capture the de-encrypted packet when receiving ESP? edit

1 Answer